在友善之臂mini2440提供的u-boot-1.1.6-FA24x0的cpu/arm920t/start.S里面，第439行有这么一段代码，它作什么用，在什么地方被使用的？
@ mike.arm9, 2006.06.24
.globl Launch
.align 4
Launch:
mov r7, r0
@ diable interrupt
@ disable watch dog timer
mov r1, #0x53000000
mov r2, #0x0
str r2, [r1]
ldr r1,=INTMSK
ldr r2,=0xffffffff @ all interrupt disable
str r2,[r1]
ldr r1,=INTSUBMSK
ldr r2,=0x7ff @ all sub interrupt disable
str r2,[r1]
ldr r1, = INTMOD
mov r2, #0x0 @ set all interrupt as IRQ (not FIQ)
str r2, [r1]
@
mov ip, #0
mcr p15, 0, ip, c13, c0, 0 @ /* zero PID */
mcr p15, 0, ip, c7, c7, 0 @ /* invalidate I,D caches */
mcr p15, 0, ip, c7, c10, 4 @ /* drain write buffer */
mcr p15, 0, ip, c8, c7, 0 @ /* invalidate I,D TLBs */
mrc p15, 0, ip, c1, c0, 0 @ /* get control register */
bic ip, ip, #0x0001 @ /* disable MMU */
mcr p15, 0, ip, c1, c0, 0 @ /* write control register */
@ MMU_EnableICache
@mrc p15,0,r1,c1,c0,0
@orr r1,r1,#(1<<12)
@mcr p15,0,r1,c1,c0,0
#ifdef CONFIG_SURPORT_WINCE
bl Wince_Port_Init
#endif
@ clear SDRAM: the end of free mem(has wince on it now) to the end of SDRAM
ldr r3, FREE_RAM_END
ldr r4, =PHYS_SDRAM_1+PHYS_SDRAM_1_SIZE @ must clear all the memory unused to zero
mov r5, #0
ldr r1, _armboot_start
ldr r2, =On_Steppingstone
sub r2, r2, r1
mov pc, r2
On_Steppingstone:
2: stmia r3!, {r5}
cmp r3, r4
bne 2b
@ set sp = 0 on sys mode
mov sp, #0
@ add by mike.arm9 2006.06.26, switch to SVC mode
msr cpsr_c, #0xdf @ set the I-bit = 1, diable the IRQ interrupt
msr cpsr_c, #0xd3 @ set the I-bit = 1, diable the IRQ interrupt
ldr sp, =0x31ff5800
nop
nop
nop
nop
mov pc, r7 @ Jump to PhysicalAddress
nop
mov pc, lr
[ 此帖被alfie2009在2009-03-17 14:44重新编辑 ]
